Detailed dynamic, geometric and supraglacial moraine data for Glaciar Pio XI, the only surge-type glacier of the Southern Patagonia Icefield

Ryan Wilson,Daniela Carrión,Andrés Rivera

doi:10.1017/aog.2016.32

Ryan Wilson, Daniela Carrión + Show 1 more

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https://doi.org/10.1017/aog.2016.32

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Abstract

ABSTRACTIn contrast to the general trend for glaciers of the Southern Patagonia Icefield, Glaciar Pio XI has experienced a large cumulative frontal advance since 1945. In an effort to better understand this advancing behaviour, this paper presents a synoptic analysis of frontal fluctuations (1998–2014), ice velocities (1986–2014), ice-surface elevations (1975–2007) and supraglacial moraines (1945–2014) derived from geospatial datasets. These analyses reveal changes in the ice flow of Glaciar Pio XI's freshwater calving northern terminus and tidewater calving southern terminus over recent decades. Between 1986 and 2000, ice flow speed generally accelerated reaching peaks of >15 m d−1 at the frontal edge of the southern terminus. Following this period, flow speed decreased, reducing to <1 m d−1 for the central part of the southern terminus in 2014, despite advancing to a neoglacial maximum. From 2000 to 2014 the reduction in speed was accompanied by a shift in maximum velocity away from the southern terminus, towards the central glacier trunk. As a result, the northern terminus, which accelerated during this period, represented the new primary flow path in 2014. Notably, the moraine maps presented highlight surges occurring around 1981 and again between 1997 and 2000, marked by arcuate moraine features on the southern terminus.

Highlights

Covering an area of 12 363 km2 from 48.5°S to 51.5°S (Arendt and others, 2015), the Southern Patagonia Icefield (SPI) forms the largest temperate ice mass in the southern hemisphere
By 2014, the frontal margins of the southern terminus had advanced to what is likely a neoglacial maximum, which is in contrast to nearby glaciers of the SPI, which have generally retreated during recent decades (Sakakibara and Sugiyama, 2014)
In an attempt to better understand the behaviour of the advancing Glaciar Pio XI, frontal positions, ice-surface elevations, ice velocities and supraglacial moraine maps, derived from various geospatial datasets, are presented over time periods ranging from 1945 to 2014

Summary

Introduction

Covering an area of 12 363 km from 48.5°S to 51.5°S (Arendt and others, 2015), the Southern Patagonia Icefield (SPI) forms the largest temperate ice mass in the southern hemisphere. Recent monitoring efforts reveal that the majority of the SPI’s outlet glaciers have undergone significant frontal retreat and thinning over the past century (Rignot and others, 2003; Sakakibara and Sugiyama, 2014). This trend of SPI mass loss is likely partly driven by long-term climatic changes. Precipitation observations in the Patagonia region have shown no significant trends over the past century, despite large interannual and interdecadal variations (Rosenblüth and others, 1995; Carrasco and others, 2002; Aravena and Luckman, 2009). A study by Rasmussen and others (2007) has shown, through a reanalysis of SPI gridded NCEP/NCAR model data that air temperature increases from 1960 to 1999 at 850 hPA may have influenced the fraction of precipitation falling as snow, reducing ice mass accumulation

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